// Base.js
module.exports = function(db) {
    this.db = db;
};
module.exports.prototype = {
    extend: function(properties) {
        var Child = module.exports;
        Child.prototype = module.exports.prototype; // [1]
        for(var key in properties) {
            Child.prototype[key] = properties[key];
        }
        return Child;
    },
    setDB: function(db) {
        this.db = db;
    },
    collection: function() {
        if(this._collection) return this._collection;
        return this._collection = this.db.collection('fastdelivery-
content');
    }
}
// 这么写的好处是，可以：var model = new (require "Base");  并且预留接口便于
定义派生对象

下面这段代码，看的我晕了半天。虽然我知道是定义一个派生对象，派生对象有
insert, update, getlist, remove这些方法。

// ContentModel.js
var Model = require("./Base"),
    crypto = require("crypto"),
    model = new Model();
var ContentModel = model.extend({  // [2]
    insert: function(data, callback) {
        data.ID = crypto.randomBytes(20).toString('hex');
        this.collection().insert(data, {}, callback || function(){ });
    },
    update: function(data, callback) {
        this.collection().update({ID: data.ID}, data, {}, callback ||
function(){ });
    },
    getlist: function(callback, query) {
        this.collection().find(query || {}).toArray(callback);
    },
    remove: function(ID, callback) {
        this.collection().findAndModify({ID: ID}, [], {}, {remove: true},
callback);
    }
});
module.exports = ContentModel;   // [3]

问题：
[1] 这行代码是否可以省略?
[2] extend方法什么时候执行？ 先于[3]语句，还是后于[3]语句。 执行extend方法
时， module.exports该指向谁？
--
修改:saynothing FROM 218.108.104.*
FROM 218.108.104.*